Slow RockShox Revs even after oil change

I have had these Dual air Revs since 2007. They used to work brilliantly with excellent small bump sensitivity. Over time they seemed to get slower, handling big bumps fine but losing responsiveness to smaller bumps. I recently changed the oil to see if that would help but they are still the same. Is this a symptom of needing to renew seals or something?

To clarify, this is not stiction, they freely move, its more like they have loads of compression damping or something.

The imbalance of pressure (more psi in top than bottom) would create a setup like this

Having the pressures equal gives the best balance of suppleness but doesn't dive under braking/steep stuff too much for me

Haing more psi in the negative preloads the positve so it goes into the travel a little, making it very supple on small stuff, but dives a lot under braking/on steep stuff/harsh bumps etc ..

If you playing with the pressures, make sure you set the top (positive) chamber first. The negative (bottom) chamber is a lot smaller so setting this first, then putting loads in the top cuases the pressure in the small negative one to ramp up far too much